Okay, so apparently almost all homemade porn ends up online:

WASHINGTON (CBS DC) – The vast majority of homemade pornography and private images on personal computers ends up on public websites called “parasites.”

Eighty-eight percent of homemade pornography, including videos and still images, finds its way onto porn sites, often without the owners’ knowledge, a new study from Britain’s Internet Watch Foundation (IWF) has found.

The study analyzed more than 12,000 sexually explicit images uploaded by young people and found that the great majority of images had been stolen and published to what the organization calls, “parasite” websites.

I cannot for the life of me understand how they came up with that figure (with, or beyond, the explanation provided).